STORY WRITTEN FOR CBS NEWS & USED WITH PERMISSION

The planned launch of a SpaceX Crew Dragon capsule Wednesday carrying four astronauts to the International Space Station has been delayed to at least Saturday because of a “minor medical issue” with one of the crew members, NASA announced Monday.

The agency said the delay is not related to COVID-19 and it is not a medical emergency, but no other details were provided. It’s not known which of the “Crew-3” astronauts — commander Raja Chari, pilot Thomas Marshburn, Kayla Barron and European Space Agency astronaut Matthias Maurer — might be affected.

The astronauts already were in quarantine, normal procedure for astronauts in the two weeks leading up to launch, and there were no indications of an issue before NASA’s announcement.

“Teams will continue to monitor crew health as they evaluate potential launch opportunities at the end of the week,” the NASA statement said. “The earliest possible opportunity for launch is 11:36 p.m. EDT Saturday, Nov. 6.”

Unlike the Russian space agency, NASA does not select and train backup crews, so all four Crew-3 astronauts must be deemed fit before the flight can proceed.

The delay is the first for a piloted NASA mission due to a medical issue since space shuttle flight STS-36 in 1990 when commander John Creighton fell ill before launch

The Crew-3 astronauts originally were scheduled for takeoff Oct. 31, but launch was delayed to early Wednesday because of stormy weather in the Atlantic Ocean along the trajectory to orbit where the crew might be forced to make an emergency splashdown during an abort.

Given the nature of the lab’s orbit, the next opportunity to launch came at 1:10 a.m. Wednesday, but NASA ruled that out with Monday’s announcement.

“The agency takes every effort to protect the crew prior to its launch through a health stabilization plan,” NASA said in its blog post. “Crew-3 astronauts will remain in quarantine at NASA’s Kennedy Space Center in Florida while preparing for their launch.”

The delay may have an impact on plans to bring four other space station astronauts back to Earth.

Launched aboard a Crew Dragon last April, the Crew-2 astronauts were planning on a “direct handover” with Chari, Marshburn, Barron and Maurer, helping their replacements get up to speed on station operations before heading back to Earth to close out a six-month stay in orbit.

But depending on how long the Crew-3 mission actually is delayed, the Crew-2 astronauts — commander Shane Kimbrough, pilot Megan McArthur, ESA astronaut Thomas Pesquet and Japanese flier Akihiko Hoshide — may be ordered home before their replacements get there.

That would temporarily leave the station in the hands of a reduced three-man crew, Soyuz MS-19/65S commander Anton Shkaplerov, cosmonaut Pyotr Dubrov and NASA astronaut Mark Vande Hei.

Shkaplerov was launched to the lab on Oct. 5 while Dubrov and Vande Hei were launched in April and plan to spend nearly a full year in orbit before returning to Earth at the end of March.